This multicenter, double blind, placebo controlled, randomized multiple dose parallel group study is designed to compare the effects of SC58635 a new non-steroidal anti-inflammatory agent, on renal function to those of naproxen. The pharmacokinetics of both agents will also be evaluated and changes in renal electrolyte excretion will be compared following single dose administration and after chronic dosing to steady state (i.e. after 7 days)